1. Field of the Invention
This invention pertains to a reclosable zipper for plastic bags which includes a peel-sealable member for attachment to the bag wall and for which a high internal force is required to open the peel seal.
2. Description of the Prior Art
In the prior art, there are a variety of reclosable bags in which the zipper interlock is augmented by a breakable or peelable seal for hermetic and/or tamper evident sealing purposes. In one such zipper a single extended flange is secured permanently to one wall and by a peelable or breakable connection to the other wall. In a double flange configuration the peel seal extends between the two flanges of the zipper. A third configuration provides the peel seal directly between the bag walls.
Such prior art however has not provided a suitable hermetic and/or tamper evident seal having a high resistance to internal opening forces which are required for many applications such as, for example where the zipper is to be used on so-called "pillow" package for chips or the like or where heavier content packages require a greater resistance to opening. As reclosable bags are used as primary packaging for an ever wider variety of products, numerous laminated films are being used for the bag material. This raises the problem of zipper-film compatibility. That is, the material used to form a zipper sealable to a film used to line a chip package may not be sealable to the film used to line a package for some other food, such as a cheese. While materials exist that are virtually universally compatible with bag films, such materials do not readily lend themselves to being extruded in the relatively complex shapes of zipper profiles.
Prior art references include U.S. Pat. No. 5,964,532 entitled "Reclosable Fastener Strip with Tamper Evident Feature" issued on Oct. 12, 1999 to St. Phillips et al.; U.S. Pat. No. 5,827,163 entitled "Method Making a Closure Arrangement for Attachment to Outside of a Bag" issued on Oct. 27, 1998 to Kettner; U.S. Pat. No. 5,725,312 entitled "Closure Arrangement Having a Peelable Seal" issued on Mar. 10, 1998 to May; U.S. Pat. No. 5,672,009 entitled Reclosable Pouch and Zipper Therefor" issued on Sep. 30, 1997 to the inventor of the present invention; U.S. Pat. No. 5,604,000 entitled "Heat-Sealable Peelable Composition" issued on Feb. 18, 1997 to May; U.S. Pat. No. 5,551,127 entitled "Closure Arrangement Having a Peelable Seal" issued on Sep. 3, 1996 to May; U.S. Pat. No. 5,513,915 entitled "Closure Arrangement Having a Breakaway Seal" issued on May 7, 1996 to May; U.S. Pat. No. 5,509,735 entitled "Closure Arrangement Having a Peelable Seal" issued on Apr. 23, 1996 to May; U.S. Pat. No. 5,492,411 entitled "Tamper Evident Peelable Seal" issued on Feb. 20, 1996 to May; U.S. Pat. No. 5,486,051 entitled "Closure Arrangement having a Breakaway Seal" issued on Jan. 23, 1996 to May; U.S. Pat. No. 5,474,382 entitled "Closure Arrangement having a Peelable Seal" issued on Dec. 12, 1995 to May; and U.S. Pat. No. 5,470,156 entitled "Closure Arrangement Having a Peelable Seal" issued on Nov. 28, 1995 to May.
U.S. Pat. No. 5,509,735 typifies the prior art in many respects and highlights the short comings of the prior art. Thus, since the profiles disclosed are joined directly to the inner surface of the bag walls, the profiles must be formed of a material that is sealable to the bag film. In addition, the peelable seal is directly subjected to the bag internal forces and hence the force the consumer must apply to break the peelable seal is the same as the internal forces of the package which the peelable seal must resist. The package must thus be made difficult for the consumer to open or the integrity of the package may be compromised.